1. Field of the Invention
The present invention relates to a fluid control module that controls the flow of fluid to a device such as a hydraulic actuator.
2. Background Information
There are many types of machines that incorporate hydraulically-driven actuators which lift or move an object. The actuator can be integrated into a hydraulic system which has a high pressure supply line, a low pressure drain line and a control valve that controls the flow of hydraulic fluid between the actuator, the supply line and the drain.
FIG. 1 shows an actuator or double-acting hydraulic cylinder 1 which has a piston 2 that separates a first cylinder chamber 3 from a second cylinder chamber 4. The piston 2 can move in either one of two directions, depending upon whether pressurized fluid is provided to the first cylinder chamber 3 or the second cylinder chamber 4. As an alternative embodiment, the actuator may include a return spring (not shown) within the first cylinder chamber 3 which moves the piston in an outward direction when the second cylinder chamber is coupled to the drain line of the system.
The actuator 1 may be controlled by a control valve 5. The control valve 5 typically contains a single three-way or four way spool valve (not shown) that can couple the cylinder chambers 3 and 4 to either a supply line 6 or a drain line 7. The control valve 5 can be actuated into either one of two states. In one state, the control valve 5 couples the first cylinder chamber 3 to the drain line 7 and allows pressurized fluid to flow into the second cylinder chamber 4 to hydraulically move the piston 2. In the other state, the valve 5 couples the second cylinder chamber 4 to the drain line 7 and allows pressurized fluid to flow into the first chamber 3 to hydraulically move the piston 2 in the opposite direction.
A control valve with a single spool only has two states. When the first cylinder chamber 3 is coupled to the supply line 6, the second cylinder chamber 4 is always coupled to the drain line 7. Likewise, when the second cylinder chamber 4 is coupled to the supply line 6, the first cylinder chamber 3 is always coupled to the drain line 7. It would be desirable to provide a control module that can provide more than two states. For example, it may be desirable to provide pressurized fluid to both cylinder chambers 3 and 4 to hold the position of the piston 2.
One embodiment of the present invention is a fluid control module that can control the flow of fluid between a rail line, a drain line, a first cylinder line and a second cylinder line. The module includes a plurality of fluid-driven valves that can couple the cylinder lines to the rail and drain lines. Each fluid-driven valve is controlled by a control valve. The module may be actuated into at least one a plurality of different states.